M. Pasteur, who has already made so many valuable discoveries in
connection with diseases that are propagated by germs, has, in his own
name and that of his assistants, MM. Chamberlan and Roux, communicated
to the French Academies of Sciences and Medicine the results of his
experimental inoculations with the virus of rabies. He finds that the
virus may remain in the nervous tissues without manifestation for
three weeks, even during the summer months. Virulence is manifested
not merely in the nervous tissues, but in the parotid and sub-lingual
glands. The granulations observed in the fourth ventricle, when in
a state of virulence, are finer than the granulations in the fourth
ventricle when in a healthy state, and they can be coloured by means
of aniline derivatives. The virus of rabies injected into the veins or
beneath the skin produces paralytic rabies, while inoculations into
the spinal cord or the brain produce the paroxysmal form. Inoculations
with quantities of the virus too small to be effective, have no
preservative influence against subsequent inoculations. Whether the
virus is propagated by means of the nervous tissues or by absorption
through the surfaces of the wound, has not been ascertained. Finally,
the experiments have shown that the protective ‘attenuation’ of the
virus is possible. The energy or the nature of the virus varies in
each species of animals. By passing the virus through different
animals, ‘cultures,’ or varying qualities of virus, are obtained, whose
precise effects can be predicted. Thus a ‘culture’ has been obtained
which certainly kills a rabbit in five or six days, and another
which certainly kills a guinea-pig in the same time. Other things
being equal, the virulence varies inversely with the duration of the
incubation. M. Pasteur and his assistants have good reason to believe
that by means of a special culture they have succeeded in making twenty
dogs absolutely proof against rabid inoculations. M. Pasteur, with his
usual caution, asks for a little longer time before finally pronouncing
on the condition of the dogs in question. To devise a means of making
the dog proof against rabies is, of course, to devise a means of almost
certainly preserving man (including children) from this frightful
disorder; for hydrophobia is almost invariably communicated to man and
other animals by the bites of rabid dogs.